A Novel LIBS Sensor for Sample Examinations on a Crime Scene

In this work, we present a compact LIBS sensor developed for characterization of samples on a crime scene following requirements of law enforcement agencies involved in the project. The sensor operates both in a tabletop mode, for aside measurements of swabbed materials or taken fragments, and in handheld mode where the sensor head is pointed directly on targets at the scene. The sensor head is connected via an umbilical to an instrument box that could be battery-powered and contains also a color camera for sample visualization, illumination LEDs, and pointing system for placing the target in focus. Here we describe the sensor's architecture and functionalities, the optimization of the acquisition parameters, and the results of some LIBS measurements. On nano-plotted traces at silica wafer and in optimized conditions, for most of the elements the detection limits, in term of the absolute element masses, were found to be below 10 picograms. We also show results obtained on some representative materials, like fingerprints, swabbed soil and gunshot residue, varnishes on metal, and coated plastics. The last, solid samples were used to evaluate the depth profiling capabilities of the instrument, where the recognition of all four car paint layers was achieved.

Artefact Profiling: Panomics Approaches for Understanding the Materiality of Written Artefacts

This review explains the strategies behind genomics, proteomics, metabolomics, metallomics and isotopolomics approaches and their applicability to written artefacts. The respective sub-chapters give an insight into the analytical procedure and the conclusions drawn from such analyses. A distinction is made between information that can be obtained from the materials used in the respective manuscript and meta-information that cannot be obtained from the manuscript itself, but from residues of organisms such as bacteria or the authors and readers. In addition, various sampling techniques are discussed in particular, which pose a special challenge in manuscripts. The focus is on high-resolution, non-targeted strategies that can be used to extract the maximum amount of information about ancient objects. The combination of the various omics disciplines (panomics) especially offers potential added value in terms of the best possible interpretations of the data received. The information obtained can be used to understand the production of ancient artefacts, to gain impressions of former living conditions, to prove their authenticity, to assess whether there is a toxic hazard in handling the manuscripts, and to be able to determine appropriate measures for their conservation and restoration.

A preliminary investigation of a two-step, non-invasive process to determine chronological deposition order of fingerprints and printed ink on paper

While traditional techniques have long allowed forensic investigators to positively identify fingermarks on documents of interest, understanding the chronological sequence of events that led to their deposition is still seen as a ‘holy grail’ for forensic examinations. By way of example, the question of whether a mark is above or below printed text is crucial. The work herein reveals that a novel application of a recently established fingermark development technique readily allows such differentiation. The process in question allies forensic gelatin lifters with RECOVER, a development system that hinges on the polymerisation of disulfur dinitride. While the latter was specifically developed in its current form for the retrieval of prints from metal surfaces exposed to extreme conditions or washing, its ability to target surface effects allows for visualisation of surface interactions on forensic gelatin lifts. Crucially, in doing so the order in which the lifted material was originally deposited is also revealed. This, therefore, permits clear elucidation of the order of deposition of printed text and fingermarks—and does so both rapidly and in a non-invasive way. This long sought-after capability has the potential to revolutionise forensic document examinations.

Surface Analysis Techniques in Forensic Science: Successes, Challenges, and Opportunities for Operational Deployment

Surface analysis techniques have rapidly evolved in the last decade. Some of these are already routinely used in forensics, such as for the detection of gunshot residue or for glass analysis. Some surface analysis approaches are attractive for their portability to the crime scene. Others can be very helpful in forensic laboratories owing to their high spatial resolution, analyte coverage, speed, and specificity. Despite this, many proposed applications of the techniques have not yet led to operational deployment. Here, we explore the application of these techniques to the most important traces commonly found in forensic casework. We highlight where there is potential to add value and outline the progress that is needed to achieve operational deployment. We consider within the scope of this review surface mass spectrometry, surface spectroscopy, and surface X-ray spectrometry. We show how these tools show great promise for the analysis of fingerprints, hair, drugs, explosives, and microtraces.

Recyclable and Reusable Natural Plant-Based Paper for Repeated Digital Printing and Unprinting

Although paperless technologies are becoming ubiquitous, paper and paper-based materials remain one of the most widely used resources, predicted to exceed an annual total of 460 million metric tons by 2030. Given the environmental challenges, deleterious impact on natural resources, and waste associated with conventional wood-based paper manufacturing, developing more sustainable strategies to source, produce, and recycle paper from natural materials is essential. Here, the development and production of reusable and recyclable paper are reported. This approach offers a pathway for easily producing natural pollen grains via ecofriendly, economical, scalable, and low-energy fabrication routes. It is demonstrated that the pollen-based paper exhibits high-quality printability, readability, and erasability, enabling its reuse. Based on the pH-responsive morphological responses of engineered pollen materials, a method for hygro stable printing and on-demand unprinting is presented. The reusability of the pollen paper renders it more advantageous than conventional single-print wood-based paper. This study thus provides possible pathways to utilize non-allergenic pollen, which is renewable and naturally abundant, as a sustainable source of reusable paper. While this work primarily deals with paper, the methods described here can be extended to produce other products such as cartons and containers for the storage and transport of liquid and solid materials.

Revealing Contamination and Sequence of Overlapping Fingerprints by Unsupervised Treatment of a Hyperspectral Secondary Ion Mass Spectrometry Dataset

Time-of-flight secondary ion mass spectrometry (ToF-SIMS) has been successfully applied for chemical imaging of overlapping fingermarks. The resulting big dataset has been treated by means of an unsupervised machine learning approach based on uniform manifold approximation and projection. The hyperspectral matrix was composed of 49 million pixels associated with 518 peaks. However, the single-pixel spectrum results in a very poor signal intensity, mostly like a barcode. Contrary to what has been reported in the literature recently, we have not applied a crude approach based on binning but a sophisticated machine learning method capable of separating the chemical signals of the two fingerprints from each other and from the substrate in which they were impressed. Moreover, using ToF-SIMS, an extremely surface-sensitive technique, the sequence of deposition of the fingerprints has been determined.

Visualisation of Amphetamine Contamination in Fingerprints Using TOF-SIMS Technique

Time-of-flight secondary ion mass spectrometry (TOF-SIMS) was applied to detect traces of amphetamine on fingerprints. In the present study, three different lift tapes and latent powder fingerprints were tested. The obtained results show that it is possible to identify traces of a drug as well as its distribution over the tested fingerprint after its transfer from the primary base onto an adhesive lifter (secondary base). Moreover, images obtained by the TOF-SIMS technique enable the observation of very small areas of the analysed fingerprint as well as the identification of micro-objects (residues of a contaminant) that were left on the fingerprint. The use of the black latent fingerprint powder did not interfere with the TOF-SIMS analysis, which makes it possible to effectively use this technique to study the traces of substances on the revealed fingerprints.

Novel O-propyl, S-propyl, and N-propyl substituted 1,4-naphthoquinones and 1,4-anthraquinones as potential fingermark development reagents for porous surfaces

Lawsone is a 2-substituted-1,4-naphthoquinone derivative, which has been proposed as an alternative to the reagents currently used for fingermark detection on porous surfaces. 2-substituted-anthraquinones, which contain an additional conjugated benzene ring, have a similar chemical structure to that of lawsone. In this study, a new series of 2-substituted-1,4-naphthoquinones and 2-substituted-1,4-anthraquinones were synthesized and completely characterized by¹ H NMR,¹³ C NMR, IR, and HPLC-TOF/MS analyses. All newly synthesized 2-substituted-1,4-quinones were investigated for their ability to develop latent fingermarks on porous surfaces, and this ability was compared with that of lawsone. Each fingermark developed was graded using an established method; thus, quantitative data were attributed to each fingermark. It has been demonstrated that the 1,4-quinones react with amino acids present in latent fingermarks on selected paper surfaces to produce faint yellow-orange impressions, which exhibit strong photoluminescence when illuminated with a forensic light source at 440 nm and observed through a red filter. None of the compounds caused background darkening. The results obtained were generally similar to those of lawsone, however, 8-dibromo-2-(propylamino)naphthalene-1,4-dione and 5,8-dibromo-2-(propylthio)naphthalene-1,4-dione yielded better results for copier paper and colored (blue) copier paper used in this analysis. To the best of our knowledge, this is the first study to examine the role of 1,4-anthraquinone derivatives as potential fingermark development reagents. The results indicate that 1,4-quinones have a potential to be used as reagents for enhancement of latent fingermarks.

Methodologies Applied to Fingerprint Analysis

This systematic review deals with the last 10 years of research in analytical methodologies for the analysis of fingerprints, regarding their chemical and biological constituents. A total of 123 manuscripts, which fit the search criteria defined using the descriptor "latent fingermarks analysis," were selected. Its main instrumental areas (mass spectrometry, spectroscopy, and innovative methods) were analyzed and summarized in a specific table, highlighting its main analytical parameters. The results show that most studies in this field use mass spectrometry to identify the constituents of fingerprints, both to determine the chemical profile and for aging. There is also a marked use of mass spectrometry coupled with chromatographic methods, and it provides accurate results for a fatty acid profile. Additional significant results are achieved by spectroscopic methods, mainly Raman and infrared. It is noteworthy that spectroscopic methods using microscopy assist in the accuracy of the analyzed region of the fingerprint, contributing to more robust results. There was also a significant increase in studies using methods focused on finding new developers or identifying components present in fingerprints by rapid tests. This systematic review of analytical techniques applied to the detection of fingerprints explores different approaches to contribute to future studies in forensic identification, verifying new demands in the forensic sciences and assisting in the selection of studies for the progress of research.

The optimisation of fingermark enhancement by VMD and Lumicyano™ on thermal paper

The enhancement of fingermarks on thermal paper can be challenging due to background staining caused by polar solvents used in fingermark enhancement techniques such as ninhydrin. This study explored a commercial one-step superglue fuming process, Lumicyano™, and Vacuum Metal Deposition (VMD) to develop fingermarks on this substrate and overcome this issue. Different sequential treatments involving Lumicyano™ and a combination of VMD methods were investigated with varying degrees of success with some sequences being highly sensitive. The VMD processes, however, were observed to generally be more effective at enhancing marks, whereas Lumicyano™ provided little or no benefit on this paper type. The results indicate that Lumicyano™ is only beneficial as a pre-treatment when the entire sequence of gold/zinc and silver/zinc is taken to completion. The gold/zinc and silver/zinc VMD processes were optimised on five different thermal papers, and the optimised techniques were then directly compared to determine which was more successful on each thermal paper type as a single treatment.